If she can't find another suitable place, that makes me believe she is paying way under market, and unfortunately when you rent those kinds of places, they come with certain challenges, such as a "hands on" landlord.Another factor that was not pointed out yet on this thread, is that the LL is an owner-occupant. 

Any recommended reading to learn more about this approach?

How long did it take for you to accumulate 9 properties and what were the challenges you faced getting there? 

Because of 2008 or knowing we approaching the top ?

This was definitely a fun project although it had it's challenges.

Or the "Rented for $900 a Month" approach. 

It's not come up yet someone challenged me with official documentation on a service animal.

I’m guessing it has less to do with the redemption period than the statutory time someone can challenge the validity of the sale.....proper notices, etc. 

If there were one problem that somebody should build an app for, what would it be? You're an investor with more than a couple doors and if you could solve this one problem, your life would be 10x easier. What is it?

For duplex they use $/sf cost and income approach.